# Mass measurement of graphene using quartz crystal microbalances

## TL;DR

This paper introduces a quartz crystal microbalance method to accurately measure the mass of graphene and contamination, enabling assessment of transfer process cleanliness and quality control in graphene fabrication.

## Contribution

A novel QCM-based technique for direct, precise measurement of graphene mass and contamination levels, improving quality assessment of transfer methods.

## Key findings

- Polymer transfer methods can increase graphene mass by tenfold.
- QCM measurements can distinguish graphene from contaminants.
- Method enables standardized testing of graphene transfer quality.

## Abstract

Current wafer-scale fabrication methods for graphene-based electronics and sensors involve the transfer of single-layer graphene by a support polymer. This often leaves some polymer residue on the graphene, which can strongly impact its electronic, thermal, and mechanical resonance properties. To assess the cleanliness of graphene fabrication methods, it is thus of considerable interest to quantify the amount of contamination on top of the graphene. Here, we present a methodology for direct measurement of the mass of the graphene sheet using quartz crystal microbalances (QCM). By monitoring the QCM resonance frequency during removal of graphene in an oxygen plasma, the total mass of the graphene and contamination is determined with sub-graphene-monolayer accuracy. Since the etch-rate of the contamination is higher than that of graphene, quantitative measurements of the mass of contaminants below, on top, and between graphene layers are obtained. We find that polymer-based dry transfer methods can increase the mass of a graphene sheet by a factor of 10. The presented mass measurement method is conceptually straightforward to interpret and can be used for standardized testing of graphene transfer procedures in order to improve the quality of graphene devices in future applications.